The Michaelis-Menten Constant for Fructose and for Glucose of Hexokinase in Bull Spermatozoa

Rikmenspoel, Robert; Caputo, Rose

doi:10.1530/jrf.0.0120437

Cited by 22 publications

(9 citation statements)

References 3 publications

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“…Moreover, the differentiated metabolic pathways for fructose and glucose lead to questions about the physiological role of fructose in dog spermatozoa. In many mammals, spermatozoa use glucose in preference to fructose when both substrates are available (Rikmenspoel and Caputo, 1966;Bedford and Hoskins, 1990;Jones and Connor, 2000). This may indicate that fructose has no relevant role in controlling the energy status of mammalian spermatozoa, as it is not the most efficient energy substrate for these cells.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, these spermatozoa can use three-carbon molecules, such as glycerol, by introducing them into the glycolytic pathway (Jones et al, 1992). However, species differ greatly in their ability to use sugars throughout the glycolytic pathway (Rikmenspoel and Caputo, 1966;Hammersted and Lardy, 1983;Jones and Connor, 2000). It is necessary to study the maintenance and regulation of the energy status of spermatozoa to understand their survival and the way by which they modulate their activity during their life cycle.…”

Section: Introductionmentioning

confidence: 99%

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Differential effects of glucose and fructose on hexose metabolism in dog spermatozoa

Rigau¹

2002

Reproduction

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ResearchIncubation of dog spermatozoa with 10 mmol l -1 glucose or fructose rapidly increased the intracellular content of glucose 6-phosphate and fructose 6-phosphate, although the effect of fructose was greater. These effects were correlated with increases in ATP, ribose 5-phosphate and glycogen contents, and in the rates of formation of Llactate and CO 2 . In all cases, except for ATP and glycogen, the effect of fructose was greater than that of glucose. The total hexokinase activity of the crude extracts of dog spermatozoa was more sensitive to fructose than to glucose at lower concentrations (0.1-3.0 mmol l -1 ). Both monosaccharides induced a fast and intense increase in the overall tyrosine phosphorylation of dog spermatozoa, although their specific induced-phosphorylation patterns differed slightly. Glut 3 and Glut 5 hexose transporters were the main hexose transporters in dog spermatozoa; however, other possible SGLT family-related hexose transporters were also localized. These data indicate that, at concentrations from 1 mmol l -1 to 10 mmol l -1 , fructose has a stronger effect than glucose on hexose metabolism of dog spermatozoa. These differences appear to be related to variations in the sensitivity of hexokinase activity. Moreover, the differential hexose metabolism induced by the two sugars had distinct effects on the function of dog spermatozoa, as revealed by the diverse patterns of tyrosine phosphorylation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Differential effects of glucose and fructose on hexose metabolism in dog spermatozoa

Rigau¹

2002

Reproduction

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“…This is based on human skeletal muscle lacking ketohexokinase (the enzyme responsible for catalysing the phosphorylation of fructose to fructose-1-phosphate). However, in addition to phosphorylating glucose, hexokinase is also able to phosphorylate fructose [76] and when fructose is infused (achieving plasma fructose concentrations of ~5.5 mmol·L −1 ) during exercise, then quantitatively important amounts of fructose (0.3–0.4 g·min −1 ) are likely to be directly oxidised by skeletal muscle [77]. Of course, this is of little relevance to sports nutrition because oral ingestion of fructose rarely results in plasma fructose concentrations exceeding ~0.4 mmol·L −1 and thus direct oxidation of fructose is negligible.…”

Section: Physiological Rationale For Glucose–fructose Co-ingestionmentioning

confidence: 99%

Glucose Plus Fructose Ingestion for Post-Exercise Recovery—Greater than the Sum of Its Parts?

et al. 2017

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Carbohydrate availability in the form of muscle and liver glycogen is an important determinant of performance during prolonged bouts of moderate- to high-intensity exercise. Therefore, when effective endurance performance is an objective on multiple occasions within a 24-h period, the restoration of endogenous glycogen stores is the principal factor determining recovery. This review considers the role of glucose–fructose co-ingestion on liver and muscle glycogen repletion following prolonged exercise. Glucose and fructose are primarily absorbed by different intestinal transport proteins; by combining the ingestion of glucose with fructose, both transport pathways are utilised, which increases the total capacity for carbohydrate absorption. Moreover, the addition of glucose to fructose ingestion facilitates intestinal fructose absorption via a currently unidentified mechanism. The co-ingestion of glucose and fructose therefore provides faster rates of carbohydrate absorption than the sum of glucose and fructose absorption rates alone. Similar metabolic effects can be achieved via the ingestion of sucrose (a disaccharide of glucose and fructose) because intestinal absorption is unlikely to be limited by sucrose hydrolysis. Carbohydrate ingestion at a rate of ≥1.2 g carbohydrate per kg body mass per hour appears to maximise post-exercise muscle glycogen repletion rates. Providing these carbohydrates in the form of glucose–fructose (sucrose) mixtures does not further enhance muscle glycogen repletion rates over glucose (polymer) ingestion alone. In contrast, liver glycogen repletion rates are approximately doubled with ingestion of glucose–fructose (sucrose) mixtures over isocaloric ingestion of glucose (polymers) alone. Furthermore, glucose plus fructose (sucrose) ingestion alleviates gastrointestinal distress when the ingestion rate approaches or exceeds the capacity for intestinal glucose absorption (~1.2 g/min). Accordingly, when rapid recovery of endogenous glycogen stores is a priority, ingesting glucose–fructose mixtures (or sucrose) at a rate of ≥1.2 g·kg body mass−1·h−1 can enhance glycogen repletion rates whilst also minimising gastrointestinal distress.

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“…In this sense, mature mammalian spermatozoa show a great ability to form lactate when incubated in the presence of hexoses such as glucose, fructose and mannose (Mann, 1975), or glycerol (Jones et al, 1992), although there are great differences between species in their ability to use sugars to form L-lactate (Rikmenspoel and Caputo, 1966;Hammersted and Lardy, 1983). However, there is a lack of information regarding how mammmalian spermatozoa manage their energy status.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a functional glycogen metabolism in mature mammalian spermatozoa

et al. 2000

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The Michaelis-Menten Constant for Fructose and for Glucose of Hexokinase in Bull Spermatozoa

Cited by 22 publications

References 3 publications

Differential effects of glucose and fructose on hexose metabolism in dog spermatozoa

Differential effects of glucose and fructose on hexose metabolism in dog spermatozoa

Glucose Plus Fructose Ingestion for Post-Exercise Recovery—Greater than the Sum of Its Parts?

Evidence for a functional glycogen metabolism in mature mammalian spermatozoa

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